Make Docker shield link to Docker hub page (hazelcast#25589)

Currently the Docker shield just links to the shield image logo which
doesn't add much value.

README.md

@@ -2,7 +2,7 @@
 
 [![Slack](https://img.shields.io/badge/slack-chat-green.svg)](https://slack.hazelcast.com/) 
 [![javadoc](https://javadoc.io/badge2/com.hazelcast/hazelcast/latest/javadoc.svg)](https://javadoc.io/doc/com.hazelcast/hazelcast/latest)
-[![Docker pulls](https://img.shields.io/docker/pulls/hazelcast/hazelcast)](https://img.shields.io/docker/pulls/hazelcast/hazelcast)
+[![Docker pulls](https://img.shields.io/docker/pulls/hazelcast/hazelcast)](https://hub.docker.com/r/hazelcast/hazelcast)
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=hazelcast_hazelcast&metric=alert_status)](https://sonarcloud.io/dashboard?id=hazelcast_hazelcast)
 
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